Apparatus for folding trailing flaps



June 24, 1958 v LABOMBARDE 2,839,972

APPARATUS FOR FOLDING TRAILING FLAPS Filed Aug. 9, 1954 I 2 Sheets-Sheet1 INVENTOR. F 29. 3. RAYMOND A. LABOMBARDE BY ATTORNEYS June 24, 1958 R.A. LABOMBARDE 2,839,972

APPARATUSFOR FOLDING TRAILING FLAPS Filed Aug. 9, 1954 2 Sheets-Sheet 2INVENTOR. RAHUOND A. LABOMBARDE P Q 011 FW A TTORNEYS 'followers andcams become worn.

United States Patent 2,839,972 APPARATUS FOR FOLDING TRAILING FLAPSRaymond A. Labombarde, Nashua, N. H.

Application August 9, 1954, Serial No. 448,720

1s Claims. or. 93- 19 This invention relates to apparatus for folding anarticulated fiap of a flat foldable article as the article is advancedat a predetermined speed along a path in a folding machine.

Many devices have heretofore been proposed for accomplishing suchfolding and this invention proposes to improve the same by simplifyingthe mechanism thereof while assuring greater accuracy and speed inoperation. In some such devices, each successive fiat article has beenstopped at one or more folding stations in a folding machine while atrailing flap of the article, such as a box blank, is folded. It will beapparent that such stops tend to slow the rate of production of themachine and that it is more desirable to accomplish the folding whilethe articles are continuously advancing at the highest speed possible.

To accomplish folding of trailing flaps while the flat articlescontinuously advance, it has been proposed to use an endless chainadvancing below the path of the articles and at the same speed, througha folding station and to provide pivoted dogs or pivoted folding fingersupstanding from the chain and engageable on 'a longitudinally extendingcam for causing the flaps'to fold. Typical of such devices are thoseshown in the U. S. Patent No. 1,980,604, of November 13, 1934, to VonThien; U. S. Patent No. 2,291,063, of July 28, 1942, to Staude; U. S.Patent No. 2,349,204, of March 16, 1944, to Staude, and U. S. Patent No.2,598,809, of June 3', 195-2, to Liebl. The folding fingers or dogs usedin this type of device are usually pivotally mounted on a link of achain and the path of the tip portion thereof may become erratic after atime, especially when the pivot pins, cam Typical of devices whichdepend on a folding finger mounted for rotation around a fixed centre ofrotation below or above the path of the articles is U. S. Patent No.2,197,089, of April 16, 1940, to Anderson, wherein the pivoted fingerfor infolding the trailing flaps of a box blank must strike the flapwith considerable impact to accomplish its folding as the blankadvances.

The principal object of this invention is to provide means for folding atrailing flap of a continuously advancing flat article such as a boxblank with a smooth gradual pressure on the flap and without the use ofpivoted folding dogs and cams for the same.

Another object of the invention is to provide folding mechanism forfolding a trailing flap of an advancing flat article such as a box blankwhich mechanism travels in an endless path but does not have parts whichrock or oscillate while following such path.

Another object of the invention is to provide trailing flap foldingmechanism capable of accomplishing a fold in an unusually small portionof the path of an advancing article thereby saving in fioor space byreducing the required length of a folding machine.

Still another object of the invention is to provide trailing flapfolding mechanism which causes a folding finger 2,839,972 Patented June24, 1958 2 i to fold by rotating the same around a centre of rotationand then advances the folding finger in the direction of advance of theflap while the flap is drawn forwardly away from the finger.

A further object of the invention is to provide an endless carrierhaving a straight stretch advancing at less speed than the speed of anadvancing article, but having a folding finger fixed thereto whichadvances at a greater speed than the article'to fold the same forwardlyas the finger rounds a parti-circular path at a spaced distance from afixed pivot.

A still further object of the invention is to provide novel flexibleholddown means for applying pressure on the line of articulation of atrailing flap as the flap is advancing and is being folded by thefolding finger of the invention, together with novel driving means forthe same.

Still further objects of the invention are to provide a folding fingercarried by an endless conveyor wherein the finger performs an importantflap holddown function, wherein a novel conveyor support is provided forthe finger, and wherein a safety release is incorporated into eachfolding finger.

Still further objects of the invention are toprovide a flap foldingmechanism so positive in operation as to eliminate the need for costlyhand pre-breaki'ng of lines of articulation in articles being folded, toalso eliminate the need for mechanical pre-breaking of the same, toreduce the weight and cost of such mechanism, and to eliminate the needfor endless chain holddown mechanism' now required by traveling,pivotable folding fingers.

Other objects and advantageous features of the invention will beapparent from the following description of the invention taken with theaccompanying drawings and it will be understood that the invention isnot confined to the exact features shown therein since various otherembodiments of the invention may be adopted "within the scope of theclaims. V

In'the drawings:

Fig. 1 is a side elevation of the endless carrier and folding finger ofthis invention folding a trailing articulated flap of an advancing flatarticle. I i

Fig. 2 is a view similar to Fig. 1 showing the article with its foldedflap drawing away from the folding finger.

Fig. 3 is a view similar to Figs. 1 and 2 of the endless carrier andfolding finger of the invention completely infolding an articulated flapof an advancing flat article in cooperation with the blank holddownmeansof the invention.

Fig. 4 is a fragmentary end view on line 44 of Fig. 3.

Fig. 5 is a view similar to Fig.3 showing the position of the parts atthe completion of an infold.

Fig. 6 is a fragmentary plan view of the device shown in Fig. 5.

Fig. 7 is a view similar to Fig. 3 showing the article with itsinfo'lded flap drawn away from the folding finger sufficiently to allowthe finger to pass downwardly below the path of the article. 1

Fig. 8 is a fragmentary side view of the driving means for the endlesscarrier and article holddown means of the invention. a

Fig. 9 is an enlarged side view of a folding finger having safetyrelease mechanism for preventing breakage under unusual stress. p

Fig. 10 is a sectional view on line 1010 of Fig. 9, and Fig. 11 is aview similar to Fig. 10 showing: the safety mechanism for the foldingfinger in released position.

In the drawings the invention is illustrated as applied to a typicalfolding machine such as are well known in the paper box, bag, envelopeand allied trades. The enillustrated wherein 21 is a foldingmachinehaving a paper line along which fiat foldable articles 22are'individually and successively advanced at a predetermined speed byequivalent, is usually provided together withsuitable elongated holddownbelts 24, all Well known in the art and forming no part of thisinvention. The paper line 20 constitute a horizontal paththrough thefolding machine and the articles 22 are usually fed to it from a stackof fiat articles in a magazine not shown. One or .more folds are madesimultaneously or successively 1n the article as it advances in thedirection of the arrows. Initially the trailing flap 26 is. fiat andconnected to the article 22 by a line of articulation 27 which lineextends transversely of the path of the articles.

The folding mechanism of this invention includes an endless carrier 28,the carrier 28 having an upper stretch 30 extending substantiallyparallel to, but at a spaced distance under, the path of the articles 22along paper line 20. The endless carrier 28 also includes a curved endstretch 31 advancing in a parti-circular path around an axis of rotationtransverse to the path of articles 22 formed by shaft 32. The endlesscarrier 28 is preferably a. roller 'chain, made up of separate links 33and may be trained around a pair of identical sprockets 34 and 35.rotatably mounted on shafts 32 and 36. The shafts 32 and 36 and thesprockets 34 and 35 are driven in any convenient manner by the drivingmechanism of the folding machine whereby the upper stretch 30 advancesat -,a lesser speed than the predetermined speed of advance of articles22. f 1 r p The' folding mechanism of the invention also includes atleastfone upstanding flap folding fingersuch as37 mountedon'the' endlesscarrier 28 and having a portion 38 adapted to'ex'tend above the path ofthe. articles 22 along paperline 20 near the end of curved end stretch31 and while travelling along upper stretch 30. It should The noted thatfinger 37-is not mounted to oscillate, pivot or otherwise change itsfixed angular relationship to the particular link 33 upon which, it isfixed and that it therefore hasno wearing parts to. become loose,vibrate or j chatter. The finger 37 is preferably of rigid material,

it may be integral with a, link 33 or aflixed. thereto by rivets, boltsor welding andpreferably it includes a fiat, comparatively broad, flapengaging surface at 39 for supporting a substantial area of a flap.

As indicated in Fig. 1, although the upper stretch 30 of endless carrier28 is travelling at less speed than the articles 22, the rotation of theterminal portion 38 of each finger 37 around the, curved end stretch 31increases its speed tomore than 'that of the articles 22 and causes the'portion 38 to fold the trailing flap 26 in the direction of advance ofthe articles. leaving thefcur'ved end stretch 31 and commencing totravel along the upper stretch 30.of endless carrier 28,

As indicated in Fig. 2, after finger 37 slows down to advance at lessspeed than the speed of advance of articles 22 along upper stretch 30,thereby lagging behind and permitting the articles to draw away and thusclearing the path for the downward rotation of the finger 37 aroundsprocket 35. While straight; finger 37 will upfold afiap to ninetydegrees for further overfolding by frictional contact with an advancingbelt, it is preferred that thefingers be forwardly inclined relative totheir base whereby partial or complete overfolding is accomplished bythe, finger alone.. v

In Figs. 31-11 the invention is illustrated as especially adapted to notonly fold a trailing flap of an advancing article but to completelyoverfold a trailing flap flatwise against the body of an article., InFig. .3 a flap folding zone of a typical folding machine is shownwherein 41 is -any convenient means, not shown, such as conveyor belts.A longitudinally extending i article support '23, or .118

thepaper line, 42 is a typical conveyor support for the flat foldablearticles 43 and 44 is a typical holddown member such as an endless belt.As is customary, the belts 42 and 44 are spaced transversely on thepaper line 41 to operate on portions of the article not being folded andto leave the portion to be folded, such as trailing flap 45, freeto bebent on its transverse line of articulation 46.

The endless carrier 47 is preferably in the form of a chain 48 made upof links 49, each link having rollers such as 50 and 51. In place of apair of sprockets for supporting the chain 48, a single toothed drivingsprocket 52 is provided mounted on a drive shaft 53. Shaft 53 issynchronized with the driving mechanism of the conveyor support 42, in awell known manner, to cause the upper stretch 54 of chain 48 to advanceat less speed than the speed of advance of articles 43. A smoothsurfaced stationary inner track 55 supports the rollers 50 and 51 of thelinks 49 as they travel around the incoming,

1 curving end stretclr56 and along the upperstretch 54,

the track 55 being formed on a plate 61. Plate 61 includes an elongatedslot 58 through which a transversely extending supporting rod 59 extendsand plate 61 is'adjustably connected to a block57 by a slot 62 in theplate and a set screw 67. Block 57 includes a hole 64 for a bearing 65,the bearing 65 being carried by a sleeve 66 integral with sprocket 52whereby the block 57 is .slidable transversely with, and supported bysprocket 52 but does not revolve with the sprocket. The plate 61 may bemoved lonigtudinally relative to block 57 by means of set screw 67 inOrder that proper tension of chain 48 may be obtained and maintained.

A pair of transversely extending threaded rods 68 and 69 are providedfor supporting block 57 and for moving the entire unit sidewis e ineither direction, as desired.

A smooth surfaced, rigid, outer track may be substantially coextensivewith the inner track 55 to support, restrain and guide the rollers 50and 51 of links 49 or preferably, as shown, to restrain, support andguide spaced extra rollers 156 mounted at the sides of certain links 49,in the folding portion of the path of the fingers.

At least one upstanding folding finger such as 70 is mounted on endlesscarrier 47 with a fixed angular relationship to a link such as 49..While finger'70 is upstanding from a link 49 with its base portion 71extending outwardly from the chain 48, the terminal portion 72 of .thefinger is bent forwardly in the direction of travel of the chain to forma hooked finger. It is this portion 72 that extends above the path ofthe articles 43 as the folding finger 70 accelerates around the curvedend stretch 56 and then decelerates to travel along upper stretch 54.Because a smooth track 55 is provided for the link rollers 50 and 51rather than a toothed sprocket, the folding action of finger 70is smoothand chattering due to the chordal or polygonic action of the chain linksor sprocket teeth is eliminated.

As shown in Fig. 3 the tip 73 of the terminal portion 72 first contactsthe underside of a trailing flap 45 and, since it is following a curvedpath around the rod 59 as a fixed centre of rotation, tip 73 travelsfaster than article 43 to not only upfold, but also overfold the flap45. As the article 43 and flap 45 advance and the portion 72 follows itscurved path above the paper line 41, the tip 73 gradually slips up thefiap 45 and the flat flap engaging surface 74 of the finger 70 comesinto contact with the flap as shown in Fig. 5..

The complete folding of a trailing fiap through an angle of by a hookedfolding finger such as 70 takes place ina short zone definedlongitudinally of the machine by the forward and rear limits of thecurved path of the terminal portion 72. It is not, therefore, necessaryto hold down the body of the blank, in alignmerit with the path of thefinger, over an elongated, extended zone by endless chain supportedholddown members as is usually necessary with pivoted endless chainfolding fingers operated by elongated cams.

Article holddown means is provided including a rigid arm 75, having asplit base 76, fixed around a shaft77, the shaft 77 being driven by anysuitable means whereby its rotation is synchronized with the speed ofconveyor 42 and endless carrier chain 48. Ann is of less length than thedistance between shaft 77 and the path of articles 43 along paper line41 in order that its terminal end 78 will not strike the advancingarticles 43. A flexible, resilient holddown member trails rearwardlyfrom the end 78 of arm 75 preferably at about a right angle thereto,member 80 being of spring metal or the like to flex upon contact with,and press resiliently down on an article 43. The terminal end 81 ofmember 80 is arranged to extend below paper line 41, if no article 43were present,

but to contact each successivearticle passing thereunder on conveyor 42with end 81 just in advance of the line of articulation 46. As arm 75rotates, the end 81 of member 80 advances with the article 43, itsterminal portion flexed upwardly and pressing down on the body of eacharticle 43 with a resilient holddown pressure. Any bow in the articles43 is thus pressed fiat while the portion 72 of fingers 70 upfold thetrailing flap 45 on line 46 and during the down fold the member 80continues in an upward rotary path out of the way of the descending flap45, as shown in Fig. 5.

As indicated in Fig. 5 the hooked, or forwardly bent, portion 72 offinger 70 performs an important flap holddown function. The portion 72,as it travels along upper stretch 54 of carrier 47 may extend parallelto the paper line 41 or may be inclined slightly upwardly therefrom, butin any case it entirely or partially overlies the folded flap 45 to holdit down in infolded position. However, since the upper stretch 54 ofchain 48 is traveling more slowly than the articles 43 on conveyor 42,the folded trailing flap 45 gradually draws awayfrom the portion 72until as indicated in Fig. 7 it is completely free thereof and entersunder a holddown bar such as 83. This occurs in time for finger 70 torotate downwardly around the outgoing, or forward end stretch 82 ofcarrier 47 without striking the flap 45 or article 43.

Preferably the driving means for holddown member 89, as shown in Fig. 8,includes a pair of enmeshed gears 84 and 85 having predetermined speedchange cycle and preferably oval, gear 84 being fixed to shaft 77 andgear 85 being carried by a shaft 86. A chain 87 is trained around asprocket 88 on shaft 86, an idler sprocket 89 and a sprocket 90, thesprocket 90 being fixed to shaft 53 which drives chain 48 of endlesscarrier 47. The oval gears cause arm 75 and member 80 to advance at thesame speed as articles 43, when member 80 is initially engaged therewithand then cause the arm 75. and member 80 to rotate rapidly out of theway of the article to clear the fingers 70 and the overfolded flap andto engage the next succeeding article 43. Two complete speed cyclechanges occur with each revolution of the gears whereby two holddownarms 75, with their flexible members 80 may be used if desired with fourfolding fingers 70 on a single carrier by suitable synchronization ofthe machine well understood in the art.

Preferably also, while the fiap folding fingers 37 or 70 are normally ata fixed anglular relationship to the portion of the carrier by whichthey are carried, and thus are normally non pivotally mounted, safetyrelease means are provided for releasing the fingers under abnormalstress. As shown in Figs. 9-11, a flap unfolding finger 91, similar tofingers 37 or 70, is provided with a tongue 92 depending from its base93, there being a correspondingly shaped, open ended V shaped groove 94facing outwardly from a bracket member 95 carried on a link 49, by boltsor the like. At least one laterally recessed ball socket 96 is providedin the tongue 92 of base 93 of finger 91, in which a ball 97 is pressedby a spring 98 mounted in a spring recess 99 intermediate of the lengthof a wall of groove 94 in bracket 95. Under normal operating conditionsthe spring pressed ball 97 holds the finger 91 in a fixed upstandingposition relative to link 49 of a chain 48. Upon a jam,'or othermalfunction occurring, however, the extra pressure on the flap engagingsurface of the finger 91 in any direction causes socket 96 to bereleased from ball 97 and permits the finger 91 to yield and slide outof the groove 94 to drop on the floor before it can damage an article 43or do damage to itself.

I claim:

1. Mechanism in a folding machine for folding a trailing articulatedflap of a fiat foldable article on a lateral fold line while the articleis continuously advanced along a path of said folding machine at apredetermined speed; said mechanism comprising an endless carrier havinga straight upper stretch extending substantially parallel to,

but under, said article path and having an incoming and an outgoingcurved end stretch each extending in a particircular path around an axisof rotation transverse to and under the said article path; meanssupporting said endless carrier in a plane normal to said article path;synchronized drive mechanism advancing said endless carrier with saidupper stretch travelling at less speed than the speed of advance of saidarticle and an upstanding flap folding finger, immovably mounted on saidendless carrier and havin a portion adapted to extend above thepath of,and forwardly in the direction of travel, of said article near the endof said incoming parti-circular path, said portion being at a spaceddistance from said axes of rotation and travelling around said incomingparticircular path at greater speed than the speed of advance of saidendless carrier to overfold a trailing flap on its lateral fold line andthereafter travelling at lesser speed than said article along the upperstretch of said endless carrier to lag behind and clear said lateralfold line before travelling around the outgoing curved end stretch ofsaid carrier.

2. Mechanism .as specified in claim 1 wherein-said-endless carrier is alink chain, said upstanding flap folding finger is non pivotally fixedto a link of the chain to maintain a constant angular relationship tothe link and the forwardly extending portion of said finger whentravelling along said upper stretch is substantially parallel theretofor holding a folded flap in overfolded position therealong.

3. Mechanism as specified in claim 1 wherein said endless carrier is aroller link chain, said flap folding finger is rigidly mounted on alink'of the chain and said carrier includes a stationery smooth tracksupporting the rollers of the chain on said incoming curved stretch andon said straight upper stretch for avoiding chordal and polygonic actionof the links of said chain during folding.

4. Mechanism as specified inclaim 1 plus an arm rotatable on an axis ofrotation transverse to, and above the path of advance of said article; aflexible holddown member trailing rearwardly from the terminal end ofsaid arm, adapted to press resiliently down on the upper surface of thearticle during part of its path, and synchronized drive means rotatingsaid arm and member in a circular path, said member being arrangedtoadvance with and resiliently hold down said article in advance-of theline of articulation of the trailing flap while said flap folding fingerfolds the flap from in rear of said line of articulation. V

5. Mechanism as specified in claim 4 wherein said flexible holddownmember and said upstanding flap folding finger both travel in a commonvertical plane longitudinally of said machine and said synchronizeddrive means includes speed change cycle gears for enabling said memberto clear said finger and the flap overfolded thereby.

6. Mechanism as specified in claim 4 wherein said synchronized drivemeans includes a pair of gears having a predetermined speed change cyclefor rotating said arm in synchronization with the rate of advance of anadvancing article to resiliently hold the article down just in advanceof said lateral fold line during overfolding and I 7 thereafter toadvance at a greater speed than the article and finger to clear the pathof said finger and flap.

7. Mechanism as specified in claim 4 wherein said synchronized drivemeans includes a pair of enmeshed oval gears, said oval gears having twospeed change cycles in each revolution thereof, for rotating two0ppositely disposed arms in synchronization with the rate of advance ofan article and the rate of advance of a flap folding fingers on saidendless carrier.

' 8.Mechanisrn as specified in claim 4 wherein said flexible holddownmember trails rearwardly from said armat substantially a right angle forresiliently pressing down a substantial longitudinal strip of an articleduring folding to flatten the same during folding.

9. Mechanism as specified in claim 4 wherein said arm is ofless lengththan the distance between its centre of rotation and the path of saidarticle but the distance between the terminal portion of said trailingmember and the arm centre of rotation is greater than the distance 'fromsaid centre to the article path whereby the terminal portion of saidmember would extend below the article pathexcept for the presence of anarticle in its path.

105 Mechanism as specified in claim 1 plus safety release means at thejunction of said upstanding flap folding finger and its endless carrierfor enabling said finger to yield under excessive stress on'saidforwardly extending portion in any angular direction in a longitudinalplane.

11. Mechanism as specified in claim 10 wherein said safety releasemeans, includes a block fixed to said carrier and provided with an openended groove extending longitudinally along and facing outwardly fromsaid carrier; a tongue depending from thebase of said folding finger,said tongue conforming in shape with, and seated in, said groove andbeing slidable endwise or outwardly from said groove and a resilient,yieldable ball and socket connection positioned intermediate of thelength of said tongue and groove for securing said tongue in said grooveunder normal stress but releasing said tongue from said groove 'underabnormal stress on said finger.

12. Mechanism as specified in claim 1 plus a ball socket at the base ofsaid finger and a spring pressed ball seated in said socket and carriedon saidendless conveyor, said spring pressed ball and socket beingarranged to normally hold said finger in a fixed position relative tothe carrier, but to release said finger from said position underabnormal stress on said forwardly extending parallel to, but below theplane of said paper line and having a curved end stretch advancing in aparticircular path around an axis of rotation transverse to, and belowsaid paper line; means supporting said chain; synchronized mechanismdriving said chain with said upper stretch advancing at-less speed thanthe speed of a blank, and a flap folding finger, having an upstandingbase portionrigidlyyand non-pivotally, fixed to a link of said carrierchain and having a terminal portion bent in the direction of travel ofsaid chain, said terminal portion describing a parti-circular path at aspaced distance from said axis of rotation and extending above the paperline near the end of said parti-circular path thereby travelling atgreater speed that the speed of said trailing flap of said blank toinfold the same forwardly and travelling at lesser speed than said blankalong the upper stretch of said chain to permit the folded flap to passfrom thereunder after such infolding.

14. Mechanism as specified in claim 13, plus an arm rotatably mountedabove the paper line on an axis of ,rotation transverse to the paperline; synchronized drive means for rotating said arm and a flexible,resilient holdof said arm, the tip of said holddown member advancingwith the line of articulation ofsaid flap and resiliently pressing downon said article during the infolding of the flap by said folding finger.

15. A device for folding forwardly a trailing flap of a flatbox blankas-said blank advances at a predetermined speed along a paper line, saiddevice comprising a pair of spaced apart sprockets rotatably mounted torevolve in a longitudinally extending, vertical plane spaced below thepath of said flap on said paper line; an endless chain trained aroundsaid sprockets and having oppositely disposed parti-circular endstretches and a horizontal upper stretch; at least one rigid hookedfinger having its base immovably fixed to a link of said chain andhaving its terminal portion bent forwardly and slightly upwardly in thedirection of travel of said chain and of said blank and means forrevolving said sprockets to advance said chain along its upper stretchat less speed than the speed of advance of said blanks, whereby theterminal portion of said finger travels at greater speed than said blankwhen rounding the parti-circular end stretch of said chain foroverfolding a flap forwardly and travels at less speed than said blankwhen advancing on the upper stretch of said chain for permitting thefolded flap to pass from thereunder after such overfolding.

16. ,A flap folding finger for use on an endless carrier to fold atrailing flap of an advancing flat article, said finger comprising ablock adapted to be fixed to an endless car rier, saidblock having alongitudinally extending V-shaped groove with each opposite end thereofopen; a folding finger of rigid material having a flap engaging portionand a base portion; a longitudinally extending tongue depending fromsaid base portion and slidably engageable in said groove, bothdownwardly and endwise thereof, a ball socket recessed laterally in saidtongue and a spring pressed ball movable laterally in one wall of saidgroove and seated in said socket for yieldably resisting the slidingmovement of said tongue in said groove.

17. An endlesscarrier for use in supporting and guiding a folding fingerin a folding machine, said carrier comprising an endless roller chain;abutting side plates on the links of said chain for preventing whipthereof, a sprockettfor supporting and driving said chain around oneloop of its path; an inner smooth stationary rigid track curved aroundthe opposite loop of said chain path and straight under the straightupper stretch thereof for supporting the rollers of said chain againstchordal, polygonic action and an outer, smooth, stationary trackextending partially along said opposite loop and along said straightstretch of said chain path for restraining said chain against outwardmovement due to centrifugal force.

s 18. A hold down device for use in paper box folding machines, saiddevice comprising an arm of rigid material adapted torotate on an axisof rotation transverse to the path of a foldable sheet through saidmachine, said arm being of less length than the distance from its axisof rotation to said sheet path and a flexible hold down member at theterminal end'of said arm, said member being adapted to trail rearwardlyfrom said terminal end during rotation ofsaid arm, at substantially aright angle thereto, and being adapted to press resiliently down on theupper face of a foldable sheet, during part of its rotational path,

, for flattening and holding down said sheet while a flap thereof isoverfolded on a lateral fold line.

References Cited in the file of this patent UNITED STATES PATENTS2,149,111 Bergstein Feb. 28, 1939 2,197,089 Anderson Apr. 16, 19402,598,809 Liebl June 3, 1952 2,641,973 Straw June 16, 1953

